Method of making polymeric acids



ale-infra United States Patent O METHOD OF MAKING POLYNIERIC ACIDS Fred 0. Barrett, Springdale, and Charles G. Goebel and Robert M. Peters, Cincinnati, Ohio, assignors to Emery Industr1es, Inc., Cincinnati, Ohio, a corporation of Ohio No Drawing. Application December 13, 1 954, 7

Serial No. 475,006

Claims. (Cl. 260-407) This invention relates to a process of manufacturing polycarboxylic fatty acids of high purity and light color Which are suitable for use in the resin industry as components of alkyd and polyamide resins. These polymeric fatty acids may also be used for many other purposes such as the manufacture of aluminum lubricating greases, and reducing the corrosiveness of gasoline.

It has long been known that polyunsaturated fatty acids such as linblenic acid, linoleic acid and their higher molecular weight homologues recovered from marine oils and the alkyl esters of these fatty acids polymerize by reaction of double bonds to form polyfunctional polymers. In general, the technical literature, including the issued patents, has advocated the polymerization of the alkyl esters of the polyunsaturated fatty acids such as methyl linoleate, as distinguished from linoleic acid, because of the degradation and impairment of color which normally attends the attempt to polymerize the acids as such. In other words, polymerization of the alkyl esters has been considered desirable because of superior yields of polymer both quantity-wise and quality-wise.

The prior literature has also advocated the use of catalysts, such as fullers earth or bentonite, preferably acid treated, or stannic chloride, to permit the use of lower temperatures and/ or shorter periods of time in the thermal process.

The object of the present invention is to provide a The present invention is based upon the discovery and determination that acid activated clays do not act to catalyze the production of thermal dimers, but rather, when properly employed as hereinafter described, they bring about the formation of an entirely different type of polymeric acid by an entirely different mechanism. The

difference in the mechanism by which the reaction proceeds, which might ordinarily be considered to be of no particular consequence as far as the end products are concerned, is in this case, of great importance. We have found that an intermediate relatively non-volatile material, apparently an inter ester, is formed during the initial heating. Superficial examination, such as determining the content of volatile and non-volatile products would lead to the erroneous conclusion that polymeric acids had been formed. We have found, however, that heating far beyond the time when the reaction would ordinarily be considered complete, is required in order to obtain polymeric acids, and we have further found that the reacting material must be acidic and that water must be present in order to obtain polymeric acids as distinguished from some other nonvolatile polymer.

In .the examination of fatty acids, fatty esters or other derivations of fatty acids, the content of free acids may be-determined by titration with a standard alkali and the grams of acidic material required to react with one equivalent weight of alkali may be termed the neutralization equivalent. If the fatty material is heated with an excess of alkali and the amount of both the free and the combined carboxylic acids is determined, then the grams of material required to react with one equivalent of alkali may be termed the saponification equivalent.

If unsaturated acids, such as linoleic or linolenic acids are heated to temperatures of 260 C. or over, a thermal polymerization will occur. If samples of the heated prodnot are subjected to vacuum distillation from time to time, as heating progresses, it will be observed that there is a steady increase in the content of non-volatile residue. Determinations of neutralization equivalent and saponification equivalent during the course of the reaction starting with around 280 for both neutralization equivalent and saponification equivalent of the original acids, will show little change in either the residues or the distillates, except for a gradual increase in both neutralization equivalent and saponification equivalent due to some destruction of carboxyl groups during the heating process. The nonvolatile residues will show essentially the same content of free carboxyl groups, that is the same neutralization equivalent as the starting material and the distillates, and the value will remain essentially constant during the entire course of the reaction.

If, on the other hand, linoleic or linolenic acids or mixtures of these acids are heated in accordance with the process of this invention, that is to approximately 230 C. in the presence of a small amount of clay and a small amount of Water, and tests for neutralization equivalent and saponification equivalent are carried out as previously described, it will be observed that the neutralization equivalent of the residue will increase slowly and after approximately one hours heating may have increased to over 400, indicating that an appreciable percentage of the original carboxyl groups are no longer free. However, the saponification equivalent will remain at essentially the starting point indicating that the carboxyl groups have not been destroyed but rather are combined in some manner, probably as esters. As the heating is continued, the neutralization equivalent drops and after 3-4 hours will have approached to within 10-15-25 points of the value for the starting material, that is, to around 300.

If the esters of the acids are used instead of the free acids, these changes are not only obscured by the absence of free acid groups by which the course of the reaction may be followed, but in addition, the esters appear to be incapable of transesterifying to form the intermediate inter ester the formation of which seems to be a necessary preliminary step to the formation of polymeric'acids. As a result, the yields of polymeric acids are much lower when esters are employed, and what yield is obtained seems to be the result of a certain amount of unavoidable hydrolysis of the ester.

It has further been determined that the presence of water is necessary in order to bring about the conversion of intermediate product, probably inter ester, to the desired polymeric acids. If the reaction is carried out in the absence. of water, the reaction progresses to the point of forming a relatively non-volatile polymeric material as evidenced by the amount and the high neutralization equivalent of the distillation residue, but in the absence of water continued heating fails to effect the decomposition of the inter ester and the liberation of the desired polymeric acids.

We have also determined that decomposition of the carboxyl groups which normally becomes evident onlyat temperatures in excess of 250-260 C. becomes quite pronounced at temperatures as low as 230 C.-in the presence of'active clays. We have further determined that this decomposition is almost completely avoided by aroaaao 3 maintaining a small percentage of water in the reacting ingredients. The water, therefore, performs two functions; it permits the desired reaction to go to completion and it prevents the undesired decomposition reactions.

The process of our invention, therefore, does not consist of merely carrying out a thermal polymerization at a lower temperature made possible by a clay catalyst but, rather, consists of a method of treating polyunsaturated acids with active clays and water to bring about first the formation of an inter ester and then the decomposition of the inter ester to form polymeric acids. These reactions are not consecutive in that one is entirely completed before the other begins but, rather, are occurring simultaneously and concurrently with the formation of inter ester predominating at the beginning of the treatment and the conversion to polymeric acids predominating at the end of the treatment.

The ditference in method of formation of the polymeric acids by the process of our invention when compared to the direct ring formation postulated for the thermal method would indicate a difierence in structural formula of the final products. An examination of the products produced by the two methods shows that the iodine value of the polymeric acids produced by our process is from 20-30 points higher than thermal polymeric acids produced from the same raw material. For example, the polymeric acids from soya fatty acids have an iodine value of 90-95 when produced by the thermal method but an iodine value of 126 when produced by the method of this invention. The iodine values may not be a true measure of the number of double bonds present, but at least they are indicative of differences in the structures of the two products.

The process of our invention, therefore, consists of heating the mixed fatty acids derived from oils or fats whose unsaturated acid content consists predominately of polyunsaturated acids with small amounts of crystalline clay mineral and small amounts of water until the neutralization equivalent of the polymerized portion approaches within 25 points, and preferably 10-15 points, of the saponification equivalent. The temperature of heating may range from 180 to 260 C., with the preferred temperature being from 215 to 240 C. The time of treatment is to a degree reversely proportional to the temperature and may range from as high as 8 hours at the lower temperatures to as low as 2 hours at the higher temperature and 3 to 4 hours at the preferred temperature. The amount of clay employed is not particularly critical except that in the case of low quality acids, a quantity in excess of the minimum required may be needed to absorb color or other impurities. The amount may, therefore, range from 1% to as high a quantity as is economically sound practice, or 20% of the weight of the acids being treated.

No water is used up in the process and that amount of water which may be used in the hydrolysis of the inter ester is subsequently liberated by further reaction. The quantity required is, therefore, small and may range from 1 to 5%. Quantities in excess of 5% are not beneficial and, in fact, are somewhat harmful as excessive water greately reduces the degree of reaction.

In general, all of the common commercial, abundant, crystalline, clay minerals may be used, such as: montmorillonite, kaolinite, hectorite, halloysite, attapulgite, sepialite. As a generality, clays vary considerably in composition, depending upon the locality of thedeposit and other factors, and many of the commercial clays are mixtures of different chemical compounds. For instance, the commercial bentonites may be used in the practice of this process if they contain suflicient montmorillonite, say 75%. Commercial clays having lesser percentages of crystalline clay mineral may be employed, but it is the crystalline clay minerals which promote the reaction. While there may be rare crystalline clay minerals-which cannot be used in this process, such clay minerals are not commercial products and are not mined for the market. All of the mined commercial crystalline clay minerals may be used in this process with good results. The bentonitic clays containing at least 75% montmorillonite are particularly recommended. Also the pH of the clay is preferably above 2 but below 7, and for best results the clay should have a pH in the neighborhood of 3 to 5. While more acid clays may be employed, their use tends to promote the formation of unsaponifiable components in the monomer.

Typical feed stocks for the use in the process of this invention include the fatty acids of linseed oil, saffiower oil, soybean oil, tall oil, cottonseed oil, corn oil, that is, the oils generally known as drying and semi-drying oils. Saturated acids which may be present do not interfere and are unchanged by the process.

The process is carried out by introducing the requisite quantities of acids, clay and water into a vessel equipped with an agitator for maintaining the clay in suspension. The vessel is preferably closed and constructed to withstand the steam pressure which will be generated at the temperature employed. Alternatively, but less desirable, a vessel equipped with a reflux condenser'to return the vaporized water may be employed. The charge is heated to the requisite temperature, usually 230-240" and held at this temperature for approximately 4 hours or until the appropriate drop in neutralization equivalent has occurred. The charge is then cooled and the pressure released to permit flashing of the water. The contents are then filtered to remove the earth and the filtrate subjected to a conventional vacuum distillation to remove the nonpolymerized portion as distillate. The polymeric acids are recovered as residue.

The following examples all involve the use of the general process just described. In these examples the I. V.s were determined by the standard Wijs method and colors by the Gardner Standards of 1933. The neutralization equivalent and saponification equivalent Were run by standard methods. All quantities and proportions which are indicated in the foregoing description and in the following examples and claims are by weight.

Example 1 Fatty acids obtained from whole soy oil by pressure splitting and bleaching but not distilling the product parts), Filtrol (4 parts) and water (2 parts) were heated in a rocking autoclave to C., and the vessel was vented to remove air. Temperature of the reaction was increased to 230 C. and maintained at 230 C. for 4 hours. The product was cooled and filtered to remove catalyst. Separation of the monomeric and polymeric acids by distillation under reduced pressure gave a polymeric acid yield of 50% of the starting acids and a monomeric acid yield of 50%. The dimeric acid had a color of 7 Gardner, a neutralization equivalent value of 304, a saponification equivalent value of 286, and an I. V. of 126; the monomeric acid had a color of less than 1 Gardner, a neutralization equivalent value of 285, a. saponification equivalent value of 281, and an I. V. of 83 Unsaponifiable contents were 0.32% and 0.74% respectively.

Example 2 Liquid cottonseed fatty acids (100 parts), Filtrol (4 parts) and water (2 parts) were heated to 120 C. at which time the autoclave was vented to remove air. The reaction was then heated to 230 C. for 4 hours, after which the partially polymerized product was cooled and filtered to remove the catalyst. Separation of polymerized material from unreacted fatty acids showed that 55% of polymeric acid and 45% unpolymerized material was present. The polymeric acid had a color of 6 Gardmet, a neutralization equivalent value of 305, a saponification equivalent value of 286, and an I. V. of whereas the monomeric acid had a color of less than 1 Gardner, a neutralization equivalent value of 298, a saponification f" K a c,

equivalent value of 281, an unsaponifiable of 0.6%, and an I. V. of 84. I

Example 3 Neutralsaponifi- Matcrinl Percent I. V. ization cation Color Equiva- Equiva- (Gardner) lent lent Fatty Acids 100 130 292 201 6 Distillate 55. 5 102 301 291 2 Residue 45. 5 149 309 293 10 No'rE.-When 2% B20 was used, the yield under above conditions was 50.5%, and when 10% Hi was used, the yield was 17.0%.

Example 4 Fatty acids (100 parts) which were derived from tall oil by rectification, fullers earth (3 parts), and water (2 parts) were heated to 260 C. for 2 hours in a rockingtype autoclave. After the 2-hour reaction period, the reaction mass was cooled to 120 C. and filtered to remove the earth catalyst. The partially polymerized fatty acids were separated by distillation under reduced pressure.

The liquid fatty acids from soya bean oil were obtained by removing the solid acid content by crystallization from solvents. The liquid acids were heated to 215 C. for 4 hours in the presence of 5% of acid activated clay and 2% of water. After heating, the autoclave in which the reaction was performed was cooled to approximately 140 C., the steam pressure was released and the product filtered to remove the clay. The filtrate was distilled under 2 mm. vacuum, 56.4% of polymeric acids having an iodine value of 137.7, a neutralization equivalent of 311.8, a saponification equivalent of 296, and a color of 7 Gardner was obtained. The acids used had an I. V. of 153.7 and a neutralization equivalent of 293 and a saponification equivalent of 285.

Example 6 Distilled safflower fatty acids were heated at 230 C. for 4 hours with 4% of Filtrol and 2% water, as described in Example 5. The results are shown in tabular form:

6 Example 7 Linseed fatty acids were processed using the same conditions as described in Example 6.

Neutral- Saponifl- Percent I. V. lzation cation Yield Equiva- Equivalent lent Linseed fatty acids 170.0 282 277 Heated product" 122. 0 291 279 Distillate 54. 8 100. 0 278 275 Polymeric Acids. 45. 2 139. 5 308 281 In general, the montmorillonite clays have been found most suitable for the practice of this process, particularly those having a pH of 3 to 5. Theseclays may have a particle size of 70 to 200 mesh, the finer sizes being preferred. Examples 1, 2, 3 and 6 disclose the use of clays of the general type described which are marketed by the Filtrol Corporation under its trademark Filtrol. This trademark is defined as follows:

Filtrol A group of acid-activated adsorbents and catalysts made from the mineral montmorillonite, (Mg,Ca)OAlz5SiOznHz0. They are supplied as fine white powders, -95% passing through a 200-mesh screen.

This definition occurs in Handbook of Material Trade Names; authors: 0. T. Zimmerman, Ph. D., and Irvin Lavine, Ph. D.; copyright 1946, 1953; published by IndustrialResearch Service, Dover, New Hampshire, 1953. When clays of this type are utilized for treating a feed stock constituted by refined fatty acids, recovered from tall oil containing, for instance, about 40% polyunsaturated acids, a high yield of polymer such as 50 to 60% is obtained. Such polymers have an I. V. in the range of 125 to 130, a saponification equivalent below 300 and a neutralization equivalent of approximately 300. However, a polymer having a neutralization equivalent not over 25 above the saponification equivalent is suitable for most purposes.

Further details of the operational procedure are provided in copending application Serial No. 475,005, filed on even date herewith, which contains claims directed to the polymerization of unsaturated fatty acids in general and the polymerization of monounsaturated fatty acids in particular.

Having described our invention, we desire to be limited only by the following claims:

1. The method of polymerizing polyunsaturated fatty acids which comprises heating parts by weight of polyunsaturated fatty acids with 26 parts crystalline clay mineral having a pH of 2-7 and about 15 parts water at a temperature of 215260 C. for a period of 25 hours, the exact time being such as to produce a polymeric residue having a neutralization equivalent between 10 and 25 units higher than its saponification equivalent.

2. The method of polymerizing polyunsaturated fatty acids which comprises heating 100 parts by weight of polyunsaturated fatty acids with 2-6 parts montmorillonite having a pH of about 3-5, and about 1-5 parts water at a temperature of 215-260 C. for a period of 2-5 hours, the exact time being such as to produce a polymeric residue having a neutralization equivalent between 10 and 25 units higher than its saponification equivalent.

3. The method of polymerizing polyunsaturated fatty acids to produce polycarboxylic fatty acids which comprises heating the polyunsaturated fatty acids and agitating them in the presence of a crystalline clay mineral having a pH of 2-7, the weight of the clay mineral being substantially 120% of the weight of the polyunsaturated fatty acids, and in the continuing presence of a small amount of water of the order of 1-5% of the weight of the polyunsaturated fatty acids until the neutralization equivalent of the polymerized products is reduced 7 to no more than 25 units higher than their saponification equivalent, the reaction being conducted in a temperature range of substantially ISO-260 C., the temperature which is utilized being sufficiently high to promote the reaction to the specified degree.

4. The method of polymerizing polyunsaturated fatty acids to produce polycarboxylic fatty acids which comprises heating the polyunsaturated fatty acids and agitating them in the presence of a crystalline clay mineral having a pH of 2-7, the weight of the clay mineral being substantially 1-20% of the weight of the polyunsaturated fatty acids, and in the continuing presence of a small amount of Water of the order of 15% of the weight of the polyunsaturated fatty acids until the neutralization equivalent of the polymerized products is reduced to no more than 25 units higher than their saponification equiv- 8 alent, the reaction being conducted in a temperature range of substantially 215-240" C., the temperature which is utilized being sufliciently high to promote the reaction to the specified degree, filtering the mixed acids to remove the clayand distilling the unreacted fatty acids from the residue.

5. The product of claim 4 wherein the polyunsaturated fatty acids are tall oil fatty acids.

References Cited in the file of this patent UNITED STATES PATENTS 2,347,562 Johnston Apr. 25, 1944 2,417,738 De Groote Mar. 18, 1947 2,482,761 Goebel Sept. 27, 1949 

3. THE METHOD OF POLYMERIZING POLYUNSATURATED FATTY ACIDS TO PRODUCE POLYCARBOXYLIC FATTY ACID WHICH COMPRISES HEATING THE POLYUNSATURATED FATTY ACIDS AND AGITATING THEN IN THE PRESENCE OF A CRYSTALLINE CLAY MINERAL HAVING A PH OF 2-7, THE WEIGHT OF THE CLAY MINERAL BEING SUBSTANTIALLY 1-20% OF THE WEIGHT OF THE POLYUNSATURATED FATTY ACIDS, AND IN THE CONTINUING PRESENCE OF A SMALL AMOUNT OF WATER OF THE ORDER OF 1-5% OF THE WEIGHT OF THE POLYUNSATURATED FATTY ACIDS UNTIL NEUTRALIZATION EQUIVALENT OF THE POLYMERIZED PRODUCTS IS REDUCED TO NO MORE THAN 25 UNITS HIGHER THAN THEIR SAPONIFICATION EQUIVALENT, THE REACTION BEING CONDUCTED IN A TEMPERATURE RANGE OF SUBSTANTIALLY 180-260*C., THE TEMPERATURE WHICH IS UTILIZED BEING SUFFICIENTLY HIGH TO PROMOTE THE REACTION TO THE SPECIFIED DEGREE. 